So, 8.5 lbs. of malt will give us our target OG in 5 gallons. Using the malt values for 85% Efficiency in Table 9, we can figure out how much of each malt to use to make up our recipe.

Malts

OG based on PPG (85%)

6.5 lbs. of 2 Row

31 x 6.5 / 5 = 40.3

0.5 lb. of Chocolate Malt

24 x .5 / 5 = 2.4

0.5 lb. of Crystal 60

29 x .5 / 5 = 2.9

0.5 lb. of Dextrin Malt

28 x .5 / 5 = 2.8

0.5 lb. of Roast Barley

22 x .5 / 5 = 2.2

8.5 lbs. total

50.6 points total

Remember though that this is the post-boil gravity. When you are collecting your wort and are wondering if you have enough, you need to ratio the measured gravity by the amount of wort you have collected to see if you will hit your target after the boil. For instance, to have 5 gallons of 1.050 wort after boiling, you would need (at least): 6 gallons of 1.042 (250 pts/6g) or 7 gallons of 1.036 (250 pts/7g)

So, when planning to brew with grain, you need to be able to figure how much malt to use if you are going to collect 6-7 gallons of wort that will boil down to 5 gallons at a target OG. (Actually you need 5.5 gallons if you plan for fermentation losses from the hops and trub.) These considerations are taken into account in Chapter 19 - Designing Recipes.

ReferencesWahl, R., Henrius, M., The American Handy Book of the Brewing, Malting, and Auxiliary Trades, Vol. 1, Chicago, 1908.